Several iCloud services are experiencing problems this afternoon, according to Apple's System Status Page.
iCloud Drive, iCloud Mail, iCloud Keychain, iCloud Contacts, iCloud Calendar, Mail Drop, Find My iPhone, and more are performing "slower than normal" for some users.
The problem has been ongoing since 8:51 a.m. Pacific Time this morning, and there's no word on when it might clear up.
If you've been noticing problems with iCloud services, this outage is the reason why. We'll update this post when the problem is resolved.